On Fri, 15 Mar 2013, Russell King - ARM Linux wrote:
On Tue, Mar 12, 2013 at 06:47:53PM -0700, Bill Huang wrote:
On Tue, 2013-03-12 at 21:40 +0800, Russell King - ARM Linux wrote:
On Tue, Mar 12, 2013 at 05:37:41AM -0700, Bill Huang wrote:
Add the below four notifier events so drivers which are interested in knowing the clock status can act accordingly. This is extremely useful in some of the DVFS (Dynamic Voltage Frequency Scaling) design.
PRE_CLK_ENABLE POST_CLK_ENABLE PRE_CLK_DISABLE POST_CLK_DISABLE
Signed-off-by: Bill Huang bilhuang@nvidia.com
NAK. *Sigh* NO, this is the wrong level to be doing stuff like this.
The *ONLY* thing that clk_prepare_enable() and clk_prepare_disable() should *EVER* be doing is calling clk_prepare(), clk_enable(), clk_disable() and clk_unprepare(). Those two functions are *merely* helpers for drivers who don't wish to make the individual calls.
Drivers are still completely free to call the individual functions, at which point your proposal breaks horribly - and they _do_ call the individual functions.
I'm proposing to give device driver a choice when it knows that some driver might be interested in knowing its clock's enabled/disabled state change at runtime, this is very important for centralized DVFS core driver. It is not meant to be covering all cases especially for drivers which is not part of the DVFS, so we don't care if it is calling clk_enable/disable directly or not.
But you're not giving drivers a choice. You're giving them an ultimatum. Either they use clk_prepare_enable() which must only be called from non- atomic contexts and have the notifiers, or if they need to use the individual functions (which is what they _should_ be doing but people are too lazy to properly convert stuff) they don't get the option of the notifiers at all.
This sucks totally, design wise.
The whole point of clk_prepare_enable() is that it is a helper function to _only_ do the clk_prepare() call followed by a clk_enable() call and _nothing_ _else_ _what_ _so_ _ever_.
If people are too lazy and start abusing clk_prepare_enable() then this helper function becomes counter-productive and should simply be removed. Same issue as with IS_ERR_OR_NULL().
Nicolas